The invention concerns and open-end spinning device with an unravelling device and two friction rollers in close proximity to each other and capable of being driven in the same direction, whereby the fibers are twisted together into a thread in the notch zone formed by said friction rollers, and furthermore concerns a thread draw-off mechanism.
In a known open-end spinning machine of the type mentioned intitially, the fiber material is unravelled into single fibers which are brought directly into the notch zone between two parallel suction drums of equal size and parallel to each other, set in close proximity to each other (DE-PS No. 2,449,583). The two suction drums rotate in the same direction and the individual fibers are fed into the notch as they fly through the air, reaching the suction zone of said suction drums in a stream that is approximately perpendicular to the plane of the axes of the two drums. The rotation of the suction drums twists the fibers together and these are then drawn off in form of a thread, in a line parallel to the drums, by a pair of draw-off drums.
However, the approximately perpendicular feeding of the fibers into the notch zone results in unsatisfactory yarn parameters, in particular with finer yarns, since the fibers are not attached regularly to the free, rotating yarn end and do not lie evenly within the yarn. Measures have therefore been proposed in the past to bring the fibers into a nearly parallel position with respect to the yarn axis when they are fed into the notch, such as by mechanical means for example, as with a whirling disk (DE-PS No. 2,720,625) or by pneumatic means such as cascade-like grading of the air pressure in the path of the fibers (DE-OS No. 2,732,678) or by feeding the fibers along a path which is inclined with respect to the thread draw-off direction, in combination with an airstream flowing essentially parallel to the thread axis. However, yarn parameters are not satisfactory in spite of these measures, especially at higher spinning speeds.
It is the object of the instant invention to create a device making it possible to control the fibers and to feed them into the notch in a parallel position, and to thereby improve the structure and solidity of the yarn.
The instant invention attains this objective with a device according to the introductory clause of claim 1, by means of a collecting surface moving parallel to the thread forming line, whereby the fibers are being fed into the notch zone over said collecting surface.
In a preferred embodiment the collecting surface is located on the periphery of a disk-like cylinder, the rotational axis of said cylinder being in a plane which is perpendicular to the notch. The peripheral speed of the collecting surface is approximately equal to the thread draw-off speed, thus making it possible to collect the full mass of fibers needed for the finished thread on the collecting surface, so that doubling of the fibers results.
A delay, together with a resulting further parallel orientation of the fibers in the notch, as well as the doubling of the fibers on the collecting surface which is increased by this delay, is obtained by giving the peripheral movement of the collecting surface a lower speed than the speed of the thread being drawn off. In order to obtain a stretching of the fibers, the peripheral speed of the collecting surface is at least equal to the feeding speed of the fibers.
Doubling therefore no longer takes place as when the fibers are fed into the gusset by means of a fiber feeding channel in the zone of rotation, but in a rotation-free zone. By thus separating rotation and doubling, a yarn of higher quality is produced.
In order to lay the arriving fibers upon the collecting surface within a precisely defined zone, the collecting surface is grooved. The width of the groove is approximately equal to the thickness of the arriving fiber material, so that a fiber formation is created which closely corresponds to the diameter of the yarn. A groove with a V-shaped cross-section is an efficient one. The fibers are held on the collecting surface by needles. Preferrably, and possibly in addition to the needles, the fibers are held on the collecting suface by pneumatic means. The division of the collecting surface into different sectors has the advantage of creating conditions to hold the fibers during conveying and for transfer into the notch zone.
The loosening of the fibers from the collecting surface in the notch zone is assisted and accelerated by an airstream flowing through the collecting surface in the area of transfer, conveying the fibers from said collecting surface into the notch zone. The airstream is produced by opening the transfer sector of the collecting surface to the atmosphere. Should this prove to be insufficient, overpressure can be brought to bear upon the transfer sector of the collecting surface. In order to maintain a defined air current within the collecting surface area, said collecting surface is enclosed within a housing.
A known unravelling device is connected before the collecting surface to ensure separation and feeding of the fiber material upon said collecting surface. The unravelling device is connected to the collecting surface through a fiber channel which is disposed essentially at a tangent to the direction of the collecting surface's movement. The outlet of the collecting surface is adapted to the width of the collecting surface.
Even greater precision in the feeding of the fibers onto the collecting surface in the direction of said collecting surface's movement is achieved if the fiber feeding channel is omitted. This is made possible by locating the housing of the unravelling roller directly next to the housing of the cylinder, the two housings being connected with each other through a connection opening which they have in common. It is practical to add a cleaning device to the collecting surface, between the point of fiber transfer into the notch area and the feeding point. Adjustability of the distance between collecting surface and thread formation line, depending upon the length of the fibers being spun together, makes it possible to adapt the device to different spinning conditions.